The invention is directed to a damping valve for a vibration damper.
In a vibration damper in a motor vehicle, a damping medium is displaced through a damping valve as a result of a movement of a suspension. The damping valve generally comprises at least one passage channel for at least one flow direction of the damping medium, which passage channel connects at least one inlet orifice and at least one outlet orifice. The outlet orifice is covered by a valve disk which is lifted slightly by the damping medium when the damping medium flows through the passage channel. A sudden pressure equalization during the lifting movement of the valve disk results in knocking noises which may be perceived as annoying by the passengers of the motor vehicle.
A damping valve for a vibration damper is known from DE 10 2010 040 458 A1. This damping valve comprises a damping valve body with separate passage channels penetrating the damping valve body for different flow directions. The passage channels connect in each instance at least one inlet orifice and at least one outlet orifice for a damping medium. The outlet orifices of the passage channels for one flow direction are connected to one another via a circular groove which is covered by at least one valve disk and is bounded radially by at least one radially outer web which has a constant width, forms a continuous support surface for the valve disk and is constructed as a closed ring. The set of problems relating to noise is to be solved in DE 10 2010 040 558 A1 in that the passage channels for one flow direction in each instance are formed at a different radial distance from the center axis of the damping valve. What is achieved by the varying distances of the passage channels from the center axis of the damping valve is primarily that the valve disk is not lifted along its entire circumference simultaneously but rather is lifted sooner than the rest of the valve disk at a location defined by the greatest distance from the center axis. As a result of the valve disk opening sooner, the sudden pressure equalization takes place at an earlier point in time when the pressure difference to be compensated is smaller than in comparable generic damping valves.
However, owing to the support surface having a constant width in a damping valve of this kind, even small amounts of liquid will cause the valve disk to stick to the valve seat and the differential pressures which are correspondingly small at low absolute pressures are not sufficient to move the valve disk. Since the generic vibration dampers generally use a liquid damping medium or at least use a lubricant, a sticking effect of the type mentioned above cannot be ruled out. This prevents the valve disk from opening at the earliest possible time.
DE 21 09 398 C3 likewise describes a damping valve for a vibration damper. This damping valve comprises a damping valve body with a plurality of separate passage channels penetrating the damping valve body for different flow directions. The passage channels for one flow direction in each instance are formed at the same radial distance from a center axis of the damping valve and connect in each instance an inlet orifice and an outlet orifice for a damping medium. The outlet orifices of the passage channels for a flow direction are connected to one another via a groove which is covered by at least one valve disk and is bounded radially by at least one radially outer web which forms a continuous support for the valve disk and is constructed as a closed ring.
In the design according to DE 21 09 398 C3, the irregular width of the support surface results in a sticking effect which has a persistent negative effect on the opening behavior of the valve disk.